How To Factor a 50 Ohm Characteristic Impedance in These Examples:

[chiques]

I have a system which has a very 'unstable' 50 Ohm characteristic impedence. I'm wondering where/how the 50 Ohms is considered in the following tutorials:

1. https://www.electronics-tutorials.ws/accircuits/series-resonance.html

2. https://www.electronics-tutorials.ws/accircuits/parallel-resonance.html


For example, in one of my system blocks, I can see the impedance changing dramatically because I'm monitoring the reflected wave (VSWR).

 

[barry]

The tutorials are speaking of impedance, which is a function of resistance, inductance and capacitance and frequency. What is your question?

 

[chiques]

My question:
How does the '50 Ohm' in a 50 Ohm system apply in these examples?

 

[barry]

?
50 ohms is the characteristic impedance of :
Your cable
Your termination impedance
Your PCB trace
...

 

[chiques]

For this discussion, I chose my trace.

 

[barry]

So, what is your question?

 

[chiques]

So, what is your question?

How do I account for the 50 Ohm impedance?

Each tutorial has an example which has a circuit resistance. It's not clear if this is the system impedance or if just a lumped resistance (30 Ohms for the series example1, 60 Ohm for the parallel example1)

In a real world RF circuit there will be a 50Ohm system impedance (typical) and a bunch of parasitics with lumped elements that can be simplified to something like this(below). I'm confused on how to calculate the characteristics based on a 50 Ohm system factoring a lumped resistive component.

 

[barry]

I don't know what you mean by "account for". Maybe this will help...
**broken link removed**

 

[chiques]

I don't know what you mean by "account for". Maybe this will help...
**broken link removed**

Yes, after I find the characteristics of the trace, how to I model it using the tutorials?

https://en.wikipedia.org/wiki/Impedance_matching#Transmission_lines

 

[biff44]

I have no idea what you are trying to do. Do you have a system block diagram, or circuit schematic you can show us. You written words are insufficient to convey what you are trying to do.

 

[chiques]

I have no idea what you are trying to do. Do you have a system block diagram, or circuit schematic you can show us. You written words are insufficient to convey what you are trying to do.

I have two types of circuits I would like to analyze, a series resonance and parallel resonance. In the academic world, analysis is fairly straight forward such as the tutorial describes. (see below)




I the RF world, systems are built to have a 50 ohm characteristic impedance.

Where does the academia analysis use the 50 Ohms? I can't imagine it can just be ignored.

 

[davenn]

you are unnecessarily complicating the tutorial problem/example
Its not asking you or telling you anything about characteristic impedance, so for the problem its irrelevant

You just have an LCR circuit with an AC voltage across it and the example showed you have to answer the questions posed
any impedance, characteristic or otherwise doesn't need to be known to answer the questions


Dave